Structural comparison of SK1 and SK2.

<p>Homology models for the catalytic domain of human SK1 and SK2 were created as described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0044543#s2" target="_blank">Materials and Methods</a> section. <b><i>A</i></b><i>)</i> The ribbon model for SK1 is shown in blue and SK2 in yellow. The expanded section highlights the extended loop found in the lipid binding domain of SK2, and bars indicate the distance between residues of SK1 and SK2. <b><i>B</i></b><i>)</i> The nucleotide and lipid binding domains of SK1 (left) and SK2 (right) were compared. Top Row: residues in the surface images of the catalytic domain are colored brown for hydrophobic and blue for hydrophilic. ADP is indicated by the ball-and-stick model, and S1P by the space-filling model. Middle Row: interaction diagrams of ADP binding to SK. Bottom Row: interaction diagrams of S1P binding to SK.